Method and apparatus for controlling the flight path angle of aircraft

ABSTRACT

A flight command system resolves an aircraft vector speed signal as a function of the vertical and horizontal components of a selected aircraft flight path angle to respectively produce commanded vertical and horizontal speed signals. The speed command signals are respectively compared with actual values of aircraft vertical and horizontal speeds to produce vertical and horizontal speed error signals, respectively, and the speed error signals indicate the deviation of the aircraft from the selected flight path angle. The system achieves vector speed control and flight path angle control simultaneously when the aircraft vector speed signal represents a desired aircraft vector speed. When a vertical path displacement error signal is combined with the commanded aircraft vertical speed signal, the system achieves flight path angle control along a specific path in space.

Unlted States Patent 1 3,698,669 Miller, deceased 51 Oct. 17, 1972 [54]METHOD AND APPARATUS FOR 3,126,474 3/1964 Zweibel et al ..244/77 A XCONTROLLING THE FLIGHT PATH 2,896,145 7/1959 Snodgrass ..244/77 D XANGLE OF AIRCRAFT P Ml B h] rima Examineriton uc er [72] Inventor:Justin G. Miller, deceased, late of 3 Examiner jefi-rey Forman Angelefiby Ann Attorney-Harold L. Jackson, Stanley R. Jones, Miner admlmstramxRobert M. Vargo and Eric T. S. Chung {73] Assignee: Lear Siegler, Inc.,Santa Monica,

Calif. [57] ABSTRACT [22] Filed; March 16 1970 A flight command systemresolves an aircraft vector speed signal as a function of the verticaland horizonl p 19,813 tal components of a selected aircraft flight pathangle to respectively produce commanded vertical and Related ApphcatlonData horizontal speed signals. The speed command signals [63]Continuation-impart of Ser, No, 845,113, M are respectively comparedwith actual values of air- 29, 1969 craft vertical and horizontal speedsto produce vertical and horizontal speed error signals, respectively,and [52] us. Cl. ..244/77 A the Speed error Signals indicate thedeviation of the 51 Int. Cl ..B64c 13/18 airereft from the selectedflight path angle The system 5 Field f Search 244/77 R 77 A, 77 318/583,achieves vector speed control and flight path angle 318/584. 343/107235/5022 control simultaneously when the aircraft vector speed signalrepresents a desired aircraft vector speed. When [56] References Cited avertical path displacement error signal is combined with the commandedaircraft vertical speed signal, the UNITED STATES PATENTS systemachieves flight path angle control along a f th 3,147,424 9/1964 Miller..244/77 D x spec pa m Space 3,295,796 1/1967 Gaylor ..244/77 A 16Claims, 5 Drawing Figures A/ECAAFT ACTUAL fZ/Gf/l' PATH AIRCRAFT VFW/LD/SPLACEME/IT I; f aflle c g spifa /t oe 9900 SOURCE i ACTUAL A IAllecleAFr. -24 l VECTOP SPEED I SEA/S02 i IMS'WUMEA/T I I PA/VELDISPLAYS i DESI/2E0 l I A/ecleArr vecm/e SPEED seuscroe I 30 1 i l ..1ACTUAL i AFCS c fir ggg I AIQCQAFT I HORIZONTAL I 76 I SPEED SE/VSOQ Lsum 2 or 3 MWJ PATENTEDucI 11 I972 PATENTEDEIBI 17 I972 SHEET 3 OF 3 x3065 QEYESQQ ms Rum 38 Ln Wow;

METHOD AND APPARATUS FOR CONTROLLING THE FLIGHT PATH ANGLE OF AIRCRAFTCROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part ofapplication Ser. No. 845,1 13, filed May 29,1969.

BACKGROUND OF THE INVENTION 1 Field of the Invention This inventionrelates to flight command systems for aircraft, and more particularly toa system for commanding an aircraft to follow a predetermined flightpath angle. The system is particularly useful for controlling the flightpath angle of vertical take-off and landing (VTOL) and vertical/shorttake-off and landing (V/STOL) aircraft.

2. Description of the Prior Art The recent increase in air trafficcongestion has emphasized the need for systems capable of assisting apilot is accurately guiding an aircraft to the terminal area. At thepresent time, instrument landing approach systems provide a radio beamor a glideslope beam which defines a fixed descent path to the landingsite, and the pilot makes an accurate terminal approach and landing bymaneuvering the aircraft to follow the glideslope beam. I

The increase in both air traffic and the speed of aircraft makes itdesirable to accurately guide aircraft to the terminal area along afixed descent path or aircraft flight path angle from locations far inadvance of the point where the glideslope beam is acquired. The use ofaircraft capable of flying a wide envelope of descent paths from cruiseflight to the terminal area increases the traffic that can beaccommodated by an airport. The need for a flight command system capableof commanding such aircraft to accurately fly a wide variety of descentpaths is apparent. Besides increasing the air traffic accommodated inthe terminal area, precise control of the aircraft flight path angleimproves fuel economy and noise abatement.

At the present time, however, aircraft are not equipped with systems fordirectly controlling flight path angle far in advance of the terminalarea. For instance, aircraft flight path angle is difficult to measureprecisely, and as a result, flight path angle information is rarely usedby the pilot for controlling the aircraft during this transition fromcruise flight to the terminal area.

SUMMARY OF THE INVENTION This invention is based on the recognition thataircraft speed information such as aircraft vector speed, horizontalspeed, or vertical speed is normally available to the pilot from sensorsaboard the aircraft. The sensed aircraft speed information is comparedwith one or more speed command signals which define a selected flightpath angle to indicate the deviation of the aircraft from the desiredflight path angle.

Briefly, the apparatus of this invention provides a system forcommanding an aircraft to maintain a selected flight path angle. Thesystem is responsive to aircraft horizontal speed, vertical speed, orvector speed, and includes means for producing a first signalrepresentative of one of the above aircraft speed components. The systemfurther includes means for producing a second signal representative of aselected aircraft flight path angle, and means responsive to the firstand second signals for producing at least one aircraft speed commandsignal representative of one of the above remaining aircraft speedcomponents. Aircraft utilization means responsive to the signalsrepresentative of two of the above aircraft speed components maintainaircraft flight along the selected flight path angle. Thus, the desiredaircraft flight path angle is selected by the pilot and the aircraftutilization means is used to maneuver the aircraft to maintain thedesired flight path angle.

In a preferred form of the invention, an aircraft vector speed signal isresolved as a function of horizontal and vertical components of theselected flight path angle to respectively produce commanded aircrafthorizontal and vertical speed signals. Sensing means produce actualspeed signals representative of the actual value of aircraft horizontaland vertical speeds, and the aircraft utilization means compares theactual speed signals with the aircraft speed command signals to producehorizontal and vertical speed error signals indicating the deviation ofthe aircraft from the selected flight path angle.

Preferably, the system of this invention provides aircraft vector speedcontrol in combination with flight path angle control when the aircraftspeed component represented by the first signal is a selected or desiredspeed component. Furthermore, this preferred system is adapted toreceive a signal in the form of a vertical path displacement errorreferenced to a specific path in space for comparison with the aircraftvertical speed error signal. The latter system achieves flightat aselected speed along a selected flight path angle defined by thespecific path in space.

The invention further contemplates a method for commanding an aircraftto maintain a selected flight path angle using an aircraft speedcomponent in the form of aircraft horizontal speed, vertical speed, orvector speed. Briefly, the method includes the steps of (a generating afirst signal which represents one of the above aircraft speedcomponents; (b generating a second signal which represents a selectedaircraft flight path angle and (c generating from the first and secondsignals at least one' aircraft speed command signal representing one ofthe 'above remaining aircraft speed components. The aircraft ismaneuvered in response to the signals representative of two of the aboveaircraft speed components for maintaining flight along the selectedflight path angle.

The flight path control provided by the apparatus and method of thisinvention is preferably used to guide an aircraft accurately from cruiseflight conditions to the terminal area where the glideslope beam isintercepted. The pilot selects the desired flight pathangle, and theresulting speed command signals are used for continuously maintainingthe aircraft on the desired angle.

The apparatus and method of this invention are particularly useful incontrolling the flight path angle of VTOL and V/STOL aircraft. At cruisespeeds the VTOL-V/STOL pitch cyclic control has a significant influenceon both longitudinal speed and vertical speed, and the VTOL-V/STOLcollective stick is generally locked in position. VTOL-V/STOL aircraftusing the system or method of this invention maintain cruise flightalong a selected flight path angle using manual or automatic pitchcyclic control to maintain the speeds required to hold the aircraft onthe desired angle.

During the transition from cruise speeds to hover speeds, the pilot ofthe VTOL-V/STOL aircraft is required to make increasingly greater use ofthe collective stick to control vertical speed, while the pitch cyclicstick is exclusively used to control longitudinal velocity. Patentapplication Ser. No. 845,113, filed May 29, 1969, discloses an aircraftcommand mixing device that schedules vertical and horizontal speedcommand information as a function of aircraft speed for application tothe pitch cyclic and collective controls of VTOL and V/STOL aircraft toreflect the above-described transition from cruise flight to hover. Theapparatus and method of this invention is adapted for use in combinationwith the collective and pitch cyclic controls of VTOL-V/STOL aircraftand with the vertical plane command mixing device for maintainingcontinuous flight path angle control from cruise flight increases thenumber of aircraft accommodated in the terminal area.

BRIEF DESCRIPTION OF THE DRAWINGS The features of specific embodimentsof the best mode contemplated of carrying out the invention areillustrated in the drawings, in which:

FIG. 1 is a block diagram showing the basic operation of the flightcommand system of this invention;

FIG. 2 is a diagram defining aircraft flight path angle;

FIG. 3 is a block diagram showing the operation ofa preferred flightcommand system;

FIG. 4 is a block diagram showing the operation of a preferred system offunction generators implementing the system of FIG. 3; and

FIG. 5 is a block diagram showing the use of this in vention inconjunction with the steering controls of a VTOL or V/STOL aircraft.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS Referring to FIGS. 1and 2, an aircraft speed signal source produces an aircraft speed signal12 representing a speed component of an aircraft 14. Preferably, speedsignal 12 represents a speed component of an aircraft 14. Preferably,speed signal 12 represents either the speed vector V of the mass centerM of the aircraft, the vertical component it, of speed vector V, or thehorizontal component V of speed vector V. flight path angle signalsource 16 produces a selected or desired flight path angle signal 18representing themagnitude of the angle between the true horizontal planeX and aircraft speed vector V.

Aircraft speed signal 12 and flight path angle signal 18 are both fed toa speed command generator 20 which produces one or more aircraft speedcommand signals 22 representing the aircraft speed component V, V, or V,resolved as a function of aircraft flight path angle. Aircraft speedcommand signals 22 are fed to aircraft utilization means 24 forcontrolling the aircraft speed component to maintain the selected flightpath angle 'y.

FIG. 3 shows preferred means for implementing the flight command systemof FIG. 1. Aircraft speed signal source 10 is represented by a sensor 26for measuring actual aircraft vector speed and for producing an outputsignal 28 representing actual aircraft vector speed. Alternatively,aircraft speed signal source 10 is represented by a selector 30 whichprovides an output signal 32 representing desired aircraft vector speed,

Typically, selector 30 comprises onboard pilot-select equipment whichallows the pilot to preselect the commanded vector speed of theaircraft. Alternatively, selector 30 can represent a flight commandcomputer programmed to provide desired vector speed information inaccordance with a particular preselected speed schedule. For example,desired aircraft vector speed signal 32 can represent a decelerationspeed schedule developed in accordance with the deceleration commandnetwork disclosed in the patent application of Justin G. Miller, Ser.No. 870,008, filed Oct. 22, 1969.

Speed command generator 20 preferably comprises a resolver 34which'receives a vector speed signal 36 having a magnitude Vrepresenting either actual aircraft vector speed signal 28 or desiredaircraft vector speed signal 32 depending upon the position of a switch38. Resolver 34 also receives a flight path angle signal 18 fromaircraft flight path angle signal source 16. Resolver 34 produces both acommanded aircraft vertical speed signal 44 having a magnitude V sin'yrepresenting the vertical speed component of aircraft vector speed Vand a commanded aircraft horizontal speed signal 46 having a magnitude Vcos 'y representing the horizontal speed component of aircraft vectorspeed V.

Commanded aircraft vertical speed signal 44 and commanded aircrafthorizontal speed signal 46 are respectively fed to a vertical speedcomparison device or summing device 48 and a horizontal speed comparisondevice or summing device 50. Summing devices 48 and 50 comprise part ofthe aircraft utilization means 24 in that they are used to determine thedeviation of the air-craft from the selected flight path angle y. Asensor 52 measures actual aircraft vertical speed and produces an outputsignal 54 having a magnitude V, which represents actual aircraftvertical speed. A sensor 56 measures actual aircraft horizontal speedand produces an output signal 58 having a magnitude V, representingactual aircraft horizontal speed. Commanded vertical speed signal 44 andactual vertical speed signal 54 are'both fed to summing device 48 whichproduces a vertical speed error signal 60 having a magnitude Ahrepresenting the algebraic difference between signals 44 and 54.Similarly, commanded horizontal speed signal 46 and actual horizontalspeed signal 58 are both fed to summing device 50 which produces ahorizontal speed error signal 62 having a magnitude AX representing thealgebraic difference between signals 46 and 58.

A vertical error comparison device or summing device 64 receives avertical path displacement error signal 66 when a switch 68 is closed.Vertical path displacement error signal 66 represents the deviation ofthe aircraft from a specific earth-referenced path in the verticalplane. This signal is produced by a vertical path displacement errorsource 70 such as an instrument landing system glideslope facility orsimilar vertical plane navigation equipment. Vertical path displace menterror signal 66 and vertical speed error signal 60 are both fed tosumming device 64 to produce a vertical control signal 72 representingthe algebraic sum of signals 60 and 66.

During use of the system shown in FIG. 3, vertical control signal 72 andhorizontal speed error signal 62 are respectively used to controlaircraft vertical and horizontal speed so that the instantaneousaircraft speed vector maintains the desired flight path angle. Dependingupon the position of a pair of ganged switches 73, signals 72 and 62 areeither fed to instrument panel displays 74 to assist the pilot inmaneuvering the aircraft along the desired angle, or they are coupled toan automatic flight control system 76 for automatically operatingaircraft controls 78. Either the instrument panel displays 74 or theautomatic flight control system 76 comprise aircraft utilization meansfor maintaining aircraft flight along the selected flight path angle asthat term is here used, in that both of these are utilization means thathave as their purpose maintaining the flight path angle. I

In use, the system shown in FIG. 3 controls the particular mode offlight along the selected flight path angle in response to the placementof switches 38 and 68. When switches 38 and 68 are placed in thepositions shown in FIG. 3, a first mode of operation. is providedwherein flight path angle control at any actual aircraft vector speed isachieved. When a desired vector speed is substituted for actual vectorspeed by placing switch 38 in the position opposite to that shown inFIG. 3, a second mode of operation is provided wherein aircraft flightpath angle and aircraft vector speed are both controlled. That is, theaircraft achieves flight along the selected flight path angle at thedesired speed simultaneously. When the second mode of operation iscombined with a vertical path displacement error by closing switch 68, athird mode of operation is provided wherein the aircraft achievesprecise flight at the desired vector speed along the particular flightpath angle defined by a specific earth-referenced path in the verticalplane.

Vector speed signals 28 and 32 represent aircraft speed command signalsin the sense that they are resolved as a function of selected flightpath angle to produce vertical and horizontal speed command signals 44and 46. Furthermore, vector speed signal 32 in its unresolved conditionis a speed command signal in the sense that it represents the desiredvector speed of the aircraft. An alternative means for maintainingflight path angle control is to resolve from vector speed signal 32either vertical speed command signal 44 or horizontal speed commandsignal 46, and to then combine vector speed signal 32 with either signal44 or signal 46 for application to aircraft utilization means tomaintain flight on the selected flight path angle.

FIG. 4 shows a preferred system of function generators for implementingthe flight command system of FIG. 3. Aircraft flight path angle signalsource 16, preferably inthe form of a potentiometer 82, produces outputsignal 18 having a magnitude proportional to the pilot selected flightpath angle 7. The selected flight path angle is then resolved into itshorizontal and vertical components by applying signal 18 to a sinegenerator 84 and a cosine generator 86. Sine generator 84 produces anoutput signal 88 having a magnitude proportional to,the sine of theflight path angle 7. Cosine generator 86 produces an output signalhaving a magnitude proportional to the cosine of the flight path angle7. Aircraft vector speed signal 36 and sine generator output signal 88are both fed to a first multiplier 90 to produce commanded aircraftvertical speed signal 44 having a magnitude proportional to the productof signals 36 and 88. Aircraft vector speed signal 36 and cosinegenerator output signal 90 are fed to a second multiplier 92 to producecommanded aircraft horizontal speed signal 46 having a magnitudeproportional to the product of signals 90 and 36. As previouslydescribed, commanded vertical and horizontal speed signals 44 and 46 arethen fed to aircraft utilization means 24 for use in maintainingaircraft flight along the selected flight path angle.

The flight command system of this invention is particularly usefulinconjunction with VTOL and V/STOL aircraft, and FIG. 5 shows anapplication of aircraft utilization means 24 which includes a collectivecommand display 94 and a pitch cyclic command display 96 of a typicalVTOL or V/STOL aircraft. A vertical plane command mixer 98 described inapplication Ser. No.

845,113, filed May 29, 1969 operates in response to aircraft vectorspeed signal 36. Vertical speed error signal 60 is routed to verticalplane command mixer 98 which schedules signal 60 as a function of vectorspeed signal 36 to produce both an output signal 100 for application tocollective command display 94 and an output signal 102 which is fed to asumming device 104. Horizontalspeed error signal 62 is routed directlyto summing device 104. Horizontal speed error signal 62 is routeddirectly to summing device l04where it is summed with output signal 102to produce a pitch control signal 106 for application to the pitchcyclic command display 96. Thus, when the flight command system of thisinvention is implemented as shown in FIG. 5, flight path angle controlfor VTOL or V/STOL aircraft is continuously maintained from cruisespeeds to hover.

The present invention has been described in the context of a preferredsystem for commanding an aircraft to fly a selected flight path angle;and it is to be understood that certain modifications of this system canbe made without departing from the scope of the invention. For example,a signal representing desired aircraft speed can be both'resolved toproduce one speed command signal and used in unresolved form as a secondspeed command signal. Both speed command signals can then be used toproduce respective error signals indicating the deviation of theaircraft from the selected flight path angle. Furthermore, aircraftvertical speed, for example, instead of aircraft vector speed, can beresolved as a function of horizontal and vector components of a selectedflight path angle to produce corresponding aircraft speed commandsignals for use in controlling the aircraft.

I claim:

1. In a VTOL or V/STOL aircraft, a system for commanding the aircraft tomaintain a Selected flight path angle, the system comprising:

a. means for producing a signal representative of aircraft speed; 4

b. means for producing a signal representative of'a selected aircraftflight path angle;

c. means responsive to the speed signal and the flight path angle signalfor resolving the speed signal into first and second components as afunction of the selected flight path angle to produce first and secondspeed commands, respectively;

d. means for producing a first and a second actual aircraft speed signalrepresentative of the actual speed of the aircraft in the directionsrepresented by the first and second speed command, respectively; and

e. means for comparing the first and second actual aircraft speedsignals with the first and second speed commands, respectively, toproduce first and second speed error signals for use in maintaining theVTOL or V/STOL aircraft on the selected flight path angle.

2. A system according to claim 1 including display means for monitoringthe first and second speed error signals.

3. A system according to claim 1 including an automatic flight controlsystem responsive to the first and second speed error signals forautomatically maintaining aircraft flight along the selected flight pathangle.

4. A system according to claim 1 wherein:

a. the speed signal is representative of aircraft vector speed;

the first and second speed commands are representative of commandedhorizontal speed and commanded vertical speed, respectively; and

c. the first and second actual aircraft speed signals arerepresentativeof actual horizontal and vertical speed of the aircraft, respectively.

5. A system according to claim 4 including:

a. horizontal speed comparison means responsive to thecommandedhorizontal speed and the actual horizontal speed for producinga horizontal speed error signal; and

. vertical speed comparison means responsive to the commanded verticalspeed and the actual vertical speed for producing a vertical speed errorsignal.

6. A system according to claim 5 including a signal representative ofthe vertical path displacement error of the aircraft with reference to adesired path in space; and including additional vertical speedcomparison means responsive to the vertical path displacement errorsignal and the vertical speed error signal for producing a verticalcontrol signal for use in maintaining flight of the aircraft along theselected flight path angle defined by the desired path in space.

7. A system according to claim 4 wherein the means for producing theaircraft speed signal is a sensor of the actual vector speed of theaircraft.

8. A system according to claim 4 wherein the means for producing theaircraft speed signal is a selector of aircraft vector speed, andwherein the VTOL or V/STOL aircraft maintains flight along the desiredflight path angle at the selected vector speed.

9. A method for commanding an aircraft to maintain a selected flightpath angle, the method including the steps of:

a. generating a signal representative of aircraft speed;

b. generating a signal representative of a selected aircraft flightangle;

c. resolving the speed signal into first and second components as afunction of the selected flight path angle to produce first and secondspeed commands, respectively;

d. generating a first and a second actual aircraft speed signalrepresentative of the actual speed of the aircraft in the directionsrepresented by the first and second speed commands, respectively;

e. comparing the first and second actual aircraft speed signals with thefirst and second speed commands, respectively, to produce first andsecond speed error signals; and

f. maneuvering the aircraft in response to the first and second errorsignals to maintain flight along the selected flight path angle.

10. A system for commanding a VTOL or V/STOL aircraft with collectivepitch and pitch cyclic steering means to maintain a selected flight pathangle, the system comprising:

a. a sensor for producing a first speed command signal representative ofaircraft vector speed;

b. a selector for producing a second signal representative of a selectedaircraft flight path angle;

c. speed command generating means for resolving from the first andsecond signals a third signal and a fourth signal representative ofcommanded aircraft horizontal speed'and vertical speed, respectively;

d. sensing means for producing a fifth signal and a sixth signalrepresentative of actual aircraft horizontal speed and vertical speed,respectively;

e. horizontal speed comparison means responsive to the third and fifthsignals for producing a horizontal speed error signal; I

f. vertical speed comparison means responsive to the fourth and sixthsignals for producing a vertical speed error signal; and

g. aircraft utilization means including means for operating thecollective pitch steering means in response to the vertical speed errorsignal and means for operating the pitch cyclic steering means inresponse to both the horizontal and vertical speed error signals so asto maintain flight of the VTOL or V/STOL aircraft along the selectedflight path angle.

11. A system according to claim 10 wherein the means for operating thecollective pitch and pitch cyclic steering means includes display meansaboard the VTOL or V/STOL aircraft for monitoring the horizontal andvertical speed error signals.

12. A system according to claim 10 wherein the means for operating thecollective pitch and pitch cyclicasteering means includes aircraftvertical plane command mixing means responsive to (i) the first speedcommand signal, (ii) the horizontal speed error signal, andtiii) thevertical speed error signal for coupling the vertical speed error signalto the collective pitch steering means as a function of the aircraftvector speed and for coupling both the vertical and horizontal speederror signals to the pitch cyclic steering means as a function of theaircraft vector speed.

13. A system for commanding an aircraft to maintain aselected flightpath angle, the system comprising:

a. means for producing a first speed command signal representative ofaircraft vector speed;

b. means for producing a second signal representafrom the first andsecond signal a third signal.

representative of commanded aircraft horizontal speed and a fourthsignal representative of commanded aircraft vertical speed;

d. sensing means for producing a fifth signal representative of actualaircraft horizontal speed and a sixth signal representative of actualaircraft vertical speed; and

e. aircraft utilization means including horizontal speed comparisonmeans responsive to the third and fifth signals for producing ahorizontal speed error signal, vertical speed comparison meansresponsive to the fourth and sixth signals for producing a verticalspeed error signal, means for generating a seventh signal representativeof the vertical path displacement error of the aircraft with referenceto a desired path in space, and means responsive to the seventh signaland the vertical speed error signal for producing a vertical controlsignal for use in conjunction with the horizontal speed error signal toachieve flight path angle control along the desired path in space.

14. A system for commanding an aircraft to maintain a selected flightpath angle, the system comprising:

d. sensing means for producing a fifth signal representative of actualaircraft horizontal speed and a sixth signal representative of actualaircraft vertical speed; and

e. aircraft utilization means including horizontal speed comparisonmeans responsive to the third and fifth signals for producing ahorizontal speed error signal, vertical speed comparison meansresponsive to the fourth and sixth signals for producing a verticalspeed error signal, collective pitch steering means and collectivecyclic steering means for a VTOL or V/STOL aircraft, the collectivepitch steering means being responsive to the vertical speed errorsignal, and the pitch steering means being responsive to both thevertical speederror signal and the horizontal speed error signal, formaintaining flight of the aircraft along the selected flight path angle.

15. A system according to claim 14 wherein the aircraft utilizationmeans further includes aircraft vertical plane command mixing meansresponsive to (i) the first speed command signal, (ii) the horizontalspeed error signal, and (iii) the vertical speed error signal forcoupling the vertical speed error signal to the collective pitchsteering means as a function of the aircraft vector speed and forcoupling the vertical speed error signal and the horizontal speed errorsignal to the pitch cyclic steering means as a function of the aircraftvector i fiq A method of commanding a VTOL or V/STOL aircraft withcollective pitch and pitch cyclic steering means to maintain a selectedflight path angle, the method including the steps of:

a. generating a first speed command signal representative of aircraftvector speed;

b. generating a second signal representative of a selected aircraftflight path angle;

c. resolving, from the first and second signals, a third signalrepresentative of commanded aircraft horizontal speed and a fourthsignal representative of commanded aircraft vertical speed;

d. generating a fifth signal representative of actual aircrafthorizontal speed and a sixth signal representative of actual aircraftvertical speed;

e. comparing the third signal with the fifth signal to produce ahorizontal speed error signal, and comparing the fourth signal with thesixth signal to produce a vertical speed error signal; and

f. maneuvering the collective pitch steering means in response to thevertical speed error signal, and maneuvering the pitch cyclic steeringmeans in response to the vertical speed error signal and the horizontalspeed error signal to maintain flight along the selected flight pathangle.

1. In a VTOL or V/STOL aircraft, a system for commanding the aircraft tomaintain a selected flight path angle, the system comprising: a. meansfor producing a signal representative of aircraft speed; b. means forproducing a signal representative of a selected aircraft flight pathangle; c. means responsive to the speed signal and the flight path anglesignal for resolving the speed signal into first and second componentsas a function of the selected flight path angle to produce first andsecond speed commands, respectively; d. means for producing a first anda second actual aircraft speed signal representative of the actual speedof the aircraft in the directions represented by the first and secondspeed command, respectively; and e. means for comparing the first andsecond actual aircraft speed signals with the first and second speedcommands, respectively, to produce first and second speed error signalsfor use in maintaining the VTOL or V/STOL aircraft on the selectedflight path angle.
 2. A system according to claim 1 including displaymeans for monitoring the first and second speed error signals.
 3. Asystem according to claim 1 including an automatic flight control systemresponsive to the first and second speed error signals for automaticallymaintaining aircraft flight along the selected flight path angle.
 4. Asystem according to claim 1 wherein: a. the speed signal isrepresentative of aircraft vector speed; b. the first and second speedcommands are representative of commanded horizontal speed and commandedvertical speed, respectively; and c. the first and second actualaircraft speed signals are representative of actual horizontal andvertical speed of the aircraft, respectively.
 5. A system according toclaim 4 including: a. horizontal speed comparison means responsive tothe commanded horizontal speed and the actual horizontal speed forproducing a horizontal speed error signal; and b. vertical speedcomparison means responsive to the commanded vertical speed and theactual vertical speed for producing a vertical speed error signal.
 6. Asystem according to claim 5 including a signal representative of thevertical path displacement error of the aircraft with reference to adesired path in space; and including additional vertical speedcomparison means responsive to the vertical path displacement errorsignal and the vertical speed error signal for producing a vErticalcontrol signal for use in maintaining flight of the aircraft along theselected flight path angle defined by the desired path in space.
 7. Asystem according to claim 4 wherein the means for producing the aircraftspeed signal is a sensor of the actual vector speed of the aircraft. 8.A system according to claim 4 wherein the means for producing theaircraft speed signal is a selector of aircraft vector speed, andwherein the VTOL or V/STOL aircraft maintains flight along the desiredflight path angle at the selected vector speed.
 9. A method forcommanding an aircraft to maintain a selected flight path angle, themethod including the steps of: a. generating a signal representative ofaircraft speed; b. generating a signal representative of a selectedaircraft flight angle; c. resolving the speed signal into first andsecond components as a function of the selected flight path angle toproduce first and second speed commands, respectively; d. generating afirst and a second actual aircraft speed signal representative of theactual speed of the aircraft in the directions represented by the firstand second speed commands, respectively; e. comparing the first andsecond actual aircraft speed signals with the first and second speedcommands, respectively, to produce first and second speed error signals;and f. maneuvering the aircraft in response to the first and seconderror signals to maintain flight along the selected flight path angle.10. A system for commanding a VTOL or V/STOL aircraft with collectivepitch and pitch cyclic steering means to maintain a selected flight pathangle, the system comprising: a. a sensor for producing a first speedcommand signal representative of aircraft vector speed; b. a selectorfor producing a second signal representative of a selected aircraftflight path angle; c. speed command generating means for resolving fromthe first and second signals a third signal and a fourth signalrepresentative of commanded aircraft horizontal speed and verticalspeed, respectively; d. sensing means for producing a fifth signal and asixth signal representative of actual aircraft horizontal speed andvertical speed, respectively; e. horizontal speed comparison meansresponsive to the third and fifth signals for producing a horizontalspeed error signal; f. vertical speed comparison means responsive to thefourth and sixth signals for producing a vertical speed error signal;and g. aircraft utilization means including means for operating thecollective pitch steering means in response to the vertical speed errorsignal and means for operating the pitch cyclic steering means inresponse to both the horizontal and vertical speed error signals so asto maintain flight of the VTOL or V/STOL aircraft along the selectedflight path angle.
 11. A system according to claim 10 wherein the meansfor operating the collective pitch and pitch cyclic steering meansincludes display means aboard the VTOL or V/STOL aircraft for monitoringthe horizontal and vertical speed error signals.
 12. A system accordingto claim 10 wherein the means for operating the collective pitch andpitch cyclic steering means includes aircraft vertical plane commandmixing means responsive to (i) the first speed command signal, (ii) thehorizontal speed error signal, and (iii) the vertical speed error signalfor coupling the vertical speed error signal to the collective pitchsteering means as a function of the aircraft vector speed and forcoupling both the vertical and horizontal speed error signals to thepitch cyclic steering means as a function of the aircraft vector speed.13. A system for commanding an aircraft to maintain a selected flightpath angle, the system comprising: a. means for producing a first speedcommand signal representative of aircraft vector speed; b. means forproducing a second signal representative of a selected aircraft flightpath angLe; c. speed command generating means for resolving from thefirst and second signal a third signal representative of commandedaircraft horizontal speed and a fourth signal representative ofcommanded aircraft vertical speed; d. sensing means for producing afifth signal representative of actual aircraft horizontal speed and asixth signal representative of actual aircraft vertical speed; and e.aircraft utilization means including horizontal speed comparison meansresponsive to the third and fifth signals for producing a horizontalspeed error signal, vertical speed comparison means responsive to thefourth and sixth signals for producing a vertical speed error signal,means for generating a seventh signal representative of the verticalpath displacement error of the aircraft with reference to a desired pathin space, and means responsive to the seventh signal and the verticalspeed error signal for producing a vertical control signal for use inconjunction with the horizontal speed error signal to achieve flightpath angle control along the desired path in space.
 14. A system forcommanding an aircraft to maintain a selected flight path angle, thesystem comprising: a. means for producing a first speed signalrepresentative of aircraft vector speed; b. means for producing a secondsignal representative of a selected aircraft flight path angle; c. speedcommand generating means for resolving from the first and second signalsa third signal representative of commanded aircraft horizontal speed anda fourth signal representative of commanded aircraft vertical speed; d.sensing means for producing a fifth signal representative of actualaircraft horizontal speed and a sixth signal representative of actualaircraft vertical speed; and e. aircraft utilization means includinghorizontal speed comparison means responsive to the third and fifthsignals for producing a horizontal speed error signal, vertical speedcomparison means responsive to the fourth and sixth signals forproducing a vertical speed error signal, collective pitch steering meansand collective cyclic steering means for a VTOL or V/STOL aircraft, thecollective pitch steering means being responsive to the vertical speederror signal, and the pitch steering means being responsive to both thevertical speed error signal and the horizontal speed error signal, formaintaining flight of the aircraft along the selected flight path angle.15. A system according to claim 14 wherein the aircraft utilizationmeans further includes aircraft vertical plane command mixing meansresponsive to (i) the first speed command signal, (ii) the horizontalspeed error signal, and (iii) the vertical speed error signal forcoupling the vertical speed error signal to the collective pitchsteering means as a function of the aircraft vector speed and forcoupling the vertical speed error signal and the horizontal speed errorsignal to the pitch cyclic steering means as a function of the aircraftvector speed.
 16. A method of commanding a VTOL or V/STOL aircraft withcollective pitch and pitch cyclic steering means to maintain a selectedflight path angle, the method including the steps of: a. generating afirst speed command signal representative of aircraft vector speed; b.generating a second signal representative of a selected aircraft flightpath angle; c. resolving, from the first and second signals, a thirdsignal representative of commanded aircraft horizontal speed and afourth signal representative of commanded aircraft vertical speed; d.generating a fifth signal representative of actual aircraft horizontalspeed and a sixth signal representative of actual aircraft verticalspeed; e. comparing the third signal with the fifth signal to produce ahorizontal speed error signal, and comparing the fourth signal with thesixth signal to produce a vertical speed error signal; and f.maneuvering the collective pitch steering means in response to theverTical speed error signal, and maneuvering the pitch cyclic steeringmeans in response to the vertical speed error signal and the horizontalspeed error signal to maintain flight along the selected flight pathangle.